In an OLED device, the conductive organic layer for emitting light is often positioned between two electrode layers (i.e., the cathode layer and the anode layer) to form a “sandwich” shaped structure. In such an OLED device, holes are injected into the organic layer from the anode and electrons are injected into the organic layer from the cathode. Holes move toward electrons and combine with electrons in the organic layer to form excitons, i.e., a bound state of electron and hole. The decay of the excitons results in relaxation of energy, accompanied by emission of radiation, e.g., visible light. Compared to conventional liquid crystal display (LCD) devices, OLED display devices do not require backlight. They are also relatively thin and light, and often have a wide viewing angle and short response time. In addition, OLED display devices generally have higher light emission efficiencies.
Meanwhile, white light OLED has been used in the OLED devices for their simple operation mechanism and voltage for cost reduction. By incorporating color filters (CF) with white light OLEDs, three primary colors, i.e., red, green, and blue can be realized. In such display panels or devices, the white light OLEDs can be used to adjust the grayscale of the units in a display panel, and the lifetimes of the OLEDs for displaying the primary colors (i.e., red, green, and blue) are the same so that color distortion caused by different lifetimes of OLEDs with different colors can be reduced.
In existing touch screen devices, parasitic capacitance may thus be formed between the cathode layer and the anode voltage lines. The parasitic capacitance may slow down the response of the touch screen to the touch motion. A touch motion may often cause the cathode voltage at or near the touch location to change and further cause the electric current flowing through the OLEDs at or near the touch location to fluctuate. As a result, the touch motion may adversely affect the display brightness or display quality of the touch screen. Also, mutual capacitance may be formed between signal lines.